In switching devices such as contactors for large loads, the magnetic field, with which the contact module is driven, is often generated directly from the switching device's input source. If the switching device is, say, fed with alternating voltage, a direct voltage is generated through a rectifier circuit, which acts as supply to a control device for the switching device. From this direct voltage, the control device generates a pulse width modulated (PWM) voltage, which is fed to one coil of the contact module.
For switching devices such as contactors for large loads, the switching process involves first activating the start-up circuit, which supplies the first PWM voltage for the contact module's start-up process to the contact module's coil. As soon as the start-up process is complete, the first PWM voltage for supplying the start-up coil is abruptly shut off and a second PWM voltage for the contact module's holding process is generated in the holding circuit, which is supplied to the contact module's coil during the switching device's holding operation.